Abstract
Plants cannot avoid being attacked by an almost infinite number of microorganisms and insects. Consequently, they arm themselves with molecular weapons against their attackers. Plant defense responses are the result of a complex signaling network, in which the hormones jasmonic acid (JA), salicylic acid (SA) and ethylene (ET) are the usual suspects under the magnifying glass when researchers investigate host-pest interactions. However, Green Leaf Volatiles (GLVs), C6 molecules, which are very quickly produced and/or emitted upon herbivory or pathogen infection by almost every green plant, also play an important role in plant defenses. GLVs are semiochemicals used by insects to find their food or their conspecifics. They have also been reported to be fundamental in indirect defenses and to have a direct effect on pests, but these are not the only roles of GLVs. These volatiles, being probably one of the fastest weapons exploited, are also able to directly elicit or prime plant defense responses. Moreover, GLVs, via crosstalk with phytohormones, mostly JA, can influence the outcome of the plant’s defense response against pathogens. For all these reasons GLVs should be considered as co-protagonists in the play between plants and their attackers.
Highlights
Plants are sessile organisms that are continuously subjected to a large number of different stresses.During some of these challenging conditions, Green Leaf Volatiles (GLVs) are produced and/or emitted
We have recently shown that a pre-treatment of Arabidopsis plants with E-2-hexenal increases susceptibility to Pseudomonas syringae pv. tomato by activating the jasmonic acid (JA)-dependent signaling pathway
Arabidopsis plants to counteract the fungus. This hypothesis is consistent with the results we found in Arabidopsis, where Pseudomonas benefits from inducing hydroperoxide lyase (HPL) by exploiting its effect on the JA
Summary
Plants are sessile organisms that are continuously subjected to a large number of different stresses. GLVs are involved in inducing plant defenses and in triggering “priming”, a state that prepares the plant to respond in an accelerated and/or augmented way to herbivory or pathogen attack [19,20,21] Another aspect that illustrates the versatility and the importance of these volatile compounds is that GLVs, by effecting mainly JA signaling or levels, can change the phytohormone dynamic equilibrium [22,23,24,25,26]. This crosstalk between phytohormones is essential in the regulation and organization of plant responses to biotic and abiotic stresses that often occur simultaneously. We want to outline the physiological importance of GLVs and to point out that they play key roles in plant defense responses
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